An exposure method for making a grating

Abstract

This invention provides an exposure method for fabricating gratings, comprising: determining the wavelength of a laser beam used in a Loehn-Morch interferometry exposure system based on the desired grating; and exposing the grating substrate to the laser beam of the stated wavelength using the Loehn-Morch interferometry exposure system. That is, given that the dimensional parameters of other components within the exposure system are constant, by adjusting the wavelength of the laser beam, the exposure area of ​​the grating substrate is prevented from falling short of the required grating area during the fabrication of the desired grating.

Description

Technical Field

[0001] This invention belongs to the field of exposure technology, and specifically relates to an exposure method for fabricating gratings. Background Technology

[0002] Holographic gratings are fabricated by creating periodic grooves on a substrate material through processes such as exposure, development, and etching. The structure of the exposure system not only limits the fabricated area of ​​the grating but also determines the quality of the grating groove shape by affecting the variation in fringe contrast. Therefore, selecting a suitable exposure system is a prerequisite for the fabrication of high-quality planar holographic gratings.

[0003] Loehn-style interferometric exposure systems are commonly used exposure systems for fabricating planar holographic gratings.

[0004] The Loewe mirror interferometric exposure system has good resistance to external disturbances, is easy to assemble and adjust, and has a stable structure. Furthermore, the beam interference angle can be easily changed by rotating the base to adjust the grating line density. However, limitations such as the size of the Loewe mirror and the aperture of the collimating lens sometimes result in the exposure area of ​​the grating substrate not meeting the required grating area during the fabrication of the desired grating. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides an exposure method for fabricating gratings.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides an exposure method for fabricating gratings, comprising the following steps:

[0008] Based on the required grating, determine the wavelength of the laser beam used in the Loewe mirror interferometric exposure system;

[0009] The Loewe mirror interferometric exposure system uses a laser beam of the specified wavelength to expose the grating substrate.

[0010] Furthermore, determining the wavelength of the laser beam used in the Loewe mirror interferometry exposure system based on the desired grating includes the following steps:

[0011] Based on the required grating area, the required grating period, and the wavelength of the laser beam currently used in the Loeux mirror interferometry system, determine the minimum size parameters of the output beam of the collimating lens of the Loeux mirror interferometry system under the size of the Loeux mirror used.

[0012] Determine whether the size of the outgoing beam from the collimating lens used in the Loehr interferometric exposure system is not less than the minimum size parameter of the outgoing beam;

[0013] If the size of the outgoing beam of the collimating lens used in the Loe mirror interferometry system is not less than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loe mirror interferometry system to fabricate the required grating is calculated based on the size of the Loe mirror, the grating area of ​​the required grating, and the grating period of the required grating.

[0014] If the size of the outgoing beam of the collimating lens used in the Loewe mirror interferometry system is smaller than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loewe mirror interferometry system to fabricate the required grating is calculated based on the minimum size parameter of the outgoing beam, the grating area of ​​the required grating, and the grating period of the required grating.

[0015] Furthermore, based on the required grating area, the required grating period, and the wavelength of the laser beam currently used in the Loehn mirror interferometry system, the minimum size parameter of the collimating lens output beam of the Loehn mirror interferometry system is determined, specifically through the following formula:

[0016] ;

[0017] in, This represents the minimum size parameter of the emitted beam. This indicates the required grating width. The grating period represents the required grating. This indicates the wavelength of the laser beam currently used in the Loewe mirror interferometry exposure system.

[0018] Furthermore, if the size of the outgoing beam from the collimating lens used in the Loewe mirror interferometry system is not less than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loewe mirror interferometry system to fabricate the required grating is calculated according to the following formula based on the size of the Loewe mirror used, the grating area of ​​the required grating, and the grating period of the required grating:

[0019] ;

[0020] in, This indicates the required grating width. The grating period represents the required grating. This indicates the length of the Loewe mirror used in the Loewe mirror interferometry exposure system. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system to create the required grating.

[0021] Furthermore, if the size of the outgoing beam from the collimating lens used in the Loewe mirror interferometry system is smaller than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loewe mirror interferometry system to fabricate the required grating is calculated using the following formula based on the minimum size parameter of the outgoing beam, the grating area of ​​the required grating, and the grating period of the required grating:

[0022] ;

[0023] in, This indicates the required grating width. The grating period represents the required grating. This represents the minimum size parameter of the emitted beam. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system to create the required grating.

[0024] Furthermore, formula (2) is derived through the following steps:

[0025] Determine the first correlation between the grating period of the required grating and the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interferometry exposure system when making the required grating;

[0026] The second correlation between the required grating width and the length of the Loewe mirror used in the Loewe mirror interferometry exposure system and the interference angle of the exposure beam is determined;

[0027] Based on the first and second association relationships, formula (2) is calculated.

[0028] Furthermore, the first correlation between the grating period of the desired grating, the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interference exposure system for fabricating the desired grating is achieved through the following formula:

[0029] ;

[0030] in, The grating period represents the required grating. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the required grating. The refractive index of the propagation medium is used in air. , This indicates the interference angle of the exposed beam.

[0031] Furthermore, the second correlation between determining the required grating width and the length of the Loewe mirror used in the Loewe mirror interference exposure system and the interference angle of the exposure beam is achieved through the following formula:

[0032] ;

[0033] in, This indicates the required grating width. This indicates the length of the Loewe mirror used in the Loewe mirror interferometry exposure system. This indicates the interference angle of the exposed beam.

[0034] Furthermore, formula (3) is derived through the following steps:

[0035] Determine the first correlation between the grating period of the required grating and the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interferometry exposure system when making the required grating;

[0036] Formula (1) combined with the first correlation relationship yields formula (3).

[0037] Furthermore, the first correlation between the grating period of the desired grating, the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interference exposure system for fabricating the desired grating is achieved through the following formula:

[0038] ;

[0039] in, The grating period represents the required grating. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the required grating. Indicates the spatial refractive index, in air, , This indicates the interference angle of the exposed beam.

[0040] Furthermore, the exposure beam uses S-polarized light.

[0041] Furthermore, formula (4) is derived through the following steps:

[0042] Determine the beam electric field of the two exposure beams in the Loehr mirror interferometric exposure system;

[0043] The total light wave of the two exposure beams in the Loe mirror interferometric exposure system is determined based on the beam electric field of the two exposure beams.

[0044] Based on the total light wave, determine the light intensity distribution value formed by the mutual interference of the two exposure beams in the Loe lens interferometric exposure system;

[0045] Based on the light intensity distribution value, formula (4) is calculated.

[0046] Furthermore, the determination of the electric field of the two exposure beams in the Loehr mirror interferometric exposure system is achieved by the following formula:

[0047] ;

[0048] in, This represents the electric field of the first exposure beam. This represents the electric field of the second exposure beam. Indicates the lateral extension direction of the grating substrate. This indicates the interference angle of the first or second exposure beam. This represents the imaginary unit in Euler's formula. This represents the light wave vector of the first or second exposure beam. The refractive index of the propagation medium is used in air. , Indicates wavelength.

[0049] Furthermore, the determination of the total light wave of the two exposure beams in the Loewe mirror interferometric exposure system based on the beam electric field of the two exposure beams is achieved by the following formula:

[0050] ;

[0051] in, This represents the total wavelength of the two exposure beams. This represents the electric field of the first exposure beam. This represents the electric field of the second exposure beam.

[0052] Furthermore, the determination of the light intensity distribution value formed by the interference of the two exposure beams in the Loehr mirror interferometric exposure system based on the total light wave is achieved by the following formula:

[0053] ;

[0054] in, This represents the light intensity distribution value formed by the interference of two exposure beams in a Loehr interferometer exposure system. This represents the total wavelength of the two exposure beams. This represents the electric field of the first exposure beam. The electric field of the second exposure beam is represented by , and the light wave vector of either the first or second exposure beam is represented by . Indicates the lateral extension direction of the grating substrate. This indicates the interference angle of the first or second exposure beam.

[0055] Furthermore, the calculation of formula (4) based on the light intensity distribution value includes the following steps:

[0056] Based on the fact that the two exposure beams in the Loehn mirror interferometry exposure system have the same light intensity, the following is obtained: ;

[0057] by replace and Substituting into formula (10), we obtain the above. ;

[0058] Substituting formula (8) into formula (11), we obtain the following: ;

[0059] Will Substituting into formula (12), we obtain the following... ;

[0060] Based on formula (13), the interference intensity of the two exposure beams is determined to be interference fringes with periodic distribution along the direction, and the interference fringe period is obtained. ;

[0061] Since the grating period is equal to the interference fringe period, then .

[0062] Furthermore, the Loewe mirror system includes a laser, a spatial filter, a collimating lens, a Loewe mirror, a grating substrate fixture, and a rotating base;

[0063] The Loe lens is perpendicular to the grating substrate clamp, with one end of the Loe lens in contact with one end of the grating substrate clamp.

[0064] The Loe lens and the grating substrate clamp are fixed together on the rotating base;

[0065] The right-angle region formed by the Loe lens and the grating substrate clamp faces the collimating lens.

[0066] Furthermore, the Loewe mirror interferometric exposure system uses a laser beam of the specified wavelength to expose the grating substrate, including the following steps:

[0067] The laser emits a laser beam of the specified wavelength. After passing through a spatial filter, the laser beam becomes a spherical wave and reaches a collimating lens. After collimation by the collimating lens, it becomes a parallel beam.

[0068] A portion of the parallel beam is used as the first beam to illuminate the Loe mirror. After being reflected by the Loe mirror, it is used as the first exposure beam to illuminate the direction of the grating substrate fixture. The other portion of the parallel beam is used as the second exposure beam to illuminate the direction of the grating substrate fixture.

[0069] The angle between the first exposure beam and the second exposure beam is adjusted by rotating the base so that the period of the interference fringes in the interference field formed by the first exposure beam and the second exposure beam meets the grating period requirements of the required grating.

[0070] A grating substrate with spin-coated photoresist is fixed on a grating substrate fixture, and the photoresist on the grating substrate undergoes interference exposure within the interference field.

[0071] Furthermore, the laser is a wavelength-tuned semiconductor laser.

[0072] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0073] This invention provides an exposure method for fabricating gratings. Based on the desired grating, the wavelength of the laser beam used in the Loehn-Morch interferometry exposure system is determined, and the Loehn-Morch interferometry exposure system uses the laser beam of the stated wavelength to expose the grating substrate. That is, given a fixed Loehn-Morch mirror size and collimating lens aperture within the Loehn-Morch interferometry exposure system, by adjusting the wavelength of the laser beam, the exposure area of ​​the grating substrate is prevented from falling short of the required grating area during the fabrication of the desired grating. Attached Figure Description

[0074] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0075] Figure 1 This is a schematic diagram of an existing Loehr mirror interferometry exposure system;

[0076] Figure 2 A schematic diagram showing the change of the exposure area of ​​a grating substrate with the periodicity of the interference fringes during an interference exposure operation on a Loehn interferometric exposure system, as an example.

[0077] Figure 3 This is a schematic diagram of the overall process of the exposure method used in this invention to fabricate the required grating;

[0078] Figure 4 This is a schematic diagram of the electric field of a beam in an exemplary Loewe mirror interferometric exposure system that uses S-polarized light to perform interferometric exposure on a grating substrate.

[0079] Among them, 1-laser, 2-spatial filter, 3-collimating lens, 4-Loe mirror, 5-grating substrate clamp, 6-rotating base. Detailed Implementation

[0080] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0081] In this document, the terms "first," "second," and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms "one," "a," and other similar words are not intended to indicate the existence of only one of the stated things, but rather that the description refers only to one of the stated things, which may have one or more. The terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0082] In this document, the terms "embodiment," "this embodiment," "preferred embodiment," and "one embodiment" do not imply that the description applies only to one specific embodiment, but rather that such description may also be applicable to one or more other embodiments. Those skilled in the art will understand that any description made herein with respect to one embodiment can be substituted, combined, or otherwise incorporated with the descriptions in one or more other embodiments. Such substitutions, combinations, or other incorporations resulting in new embodiments are readily conceived by those skilled in the art and fall within the scope of protection of this invention.

[0083] In this description, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0084] Gratings are typically fabricated by forming periodic grooves on a grating substrate material through processes such as exposure, development, and etching. The structure of existing exposure systems limits the grating fabrication area. For example, in a Loehn mirror interferometry system, limitations such as the size of the Loehn mirror and the aperture of the collimating lens sometimes result in the exposure area of ​​the grating substrate not meeting the required grating area.

[0085] like Figure 1 The diagram shows a Loehn-style interferometric exposure system, which includes a laser 1, a spatial filter 2, a collimating lens 3, a Loehn-style mirror 4, a grating substrate clamp 5, and a rotating base 6. The Loehn-style mirror 4 is perpendicular to the grating substrate clamp 5, with one end of the mirror 4 contacting the other end of the clamp 5. The Loehn-style mirror 4 and the grating substrate clamp 5 are integrally fixed to the rotating base 6, with one side of the right angle formed by the mirror 4 and the clamp 5 facing the collimating lens 3.

[0086] The process of using the Loewe mirror interferometric exposure system to perform interferometric exposure on the grating substrate is roughly as follows:

[0087] The laser beam emitted by laser 1 is converted into a spherical wave after passing through spatial filter 2 and reaches collimating lens 3. After collimation, it becomes a parallel beam (plane wave). Part of the parallel beam is used as the first beam to illuminate the Loe mirror 4. After being reflected by the Loe mirror 4, it is used as the first exposure beam to illuminate the direction of grating substrate fixture 5. The other part of the parallel beam is used as the second exposure beam to illuminate the direction of grating substrate fixture 5. The angle between the first exposure beam and the second exposure beam is adjusted by rotating base 6 so that the period of the interference fringes in the interference field formed by the first exposure beam and the second exposure beam meets the grating period requirements of the required grating. The spin-coated photoresist grating substrate is fixed on grating substrate fixture 5, and the photoresist on the grating substrate is subjected to interference exposure in the interference field.

[0088] like Figure 2 The image shows an example of a Loewe mirror interferometry system (the laser beam wavelength is 397 nm, and the Loewe mirror's length × width is 200 × 100 mm). 2 The exit dimension of the collimating lens is 300mm. 2 A schematic diagram showing the change in the exposure area of ​​a grating substrate as a function of the interference fringe period during an interference exposure operation; in the diagram, d represents the interference fringe period, L... G The figure shows the exposure width of the grating substrate. The dashed line represents the change in the exposure area of ​​the grating substrate with the interference fringe period under the constraint of the output beam size of the collimating lens, while the solid line represents the change in the exposure area of ​​the grating substrate with the interference fringe period under the constraint of the Loehn mirror length. As can be seen from the figure, regardless of whether the limitation is due to the length of the Loehn mirror or the output beam size of the collimating lens, the exposure width of the grating substrate gradually decreases as the interference fringe period increases.

[0089] To address the aforementioned problems, this invention provides an exposure method for fabricating gratings, which generally includes the following steps:

[0090] Based on the required grating, determine the wavelength of the laser beam used in the exposure system.

[0091] The exposure system uses a laser beam of the specified wavelength to expose the grating substrate.

[0092] Taking the Loehr interferometer exposure system as an example, such as Figure 3 As shown,

[0093] The exposure method used to create gratings generally includes the following steps:

[0094] Based on the required grating, the wavelength of the laser beam used in the Loewe mirror interferometry exposure system is determined. The required grating is the grating to be prepared.

[0095] The Loewe mirror interferometric exposure system uses a laser beam of the aforementioned wavelength to expose the grating substrate.

[0096] For the above-mentioned determination of the wavelength of the laser beam used in the Loehn mirror interferometry exposure system based on the required grating, exemplary steps include the following:

[0097] S1 determines the minimum size parameters of the collimating lens output beam of the Loeux mirror interferometry system under the Loeux mirror size, based on the required grating area, the required grating period, and the wavelength of the laser beam currently used in the Loeux mirror interferometry system.

[0098] For example, this can be achieved using the following formula:

[0099] ;

[0100] in, This represents the minimum size parameter of the emitted beam from the collimating lens. This indicates the required grating width. The grating period represents the required grating. This indicates the wavelength of the laser beam currently used in the Loewe mirror interferometry exposure system.

[0101] S2 determines whether the size of the outgoing beam from the collimating lens used in the Loewe mirror interferometric exposure system is not less than the minimum size parameter of the outgoing beam.

[0102] S3 When the size of the outgoing beam from the collimating lens used in the Loeux mirror interferometry system is not less than the minimum size parameter of the outgoing beam mentioned above, the wavelength of the laser beam used by the Loeux mirror interferometry system to fabricate the required grating is calculated based on the size of the Loeux mirror, the grating area of ​​the required grating, and the grating period of the required grating.

[0103] For example, the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the desired grating can be calculated using the following formula:

[0104] ;

[0105] in, This indicates the required grating width. The grating period represents the required grating. This indicates the length of the Loewe mirror used in the Loewe mirror interferometry exposure system. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system to create the required grating.

[0106] S4 When the size of the outgoing beam from the collimating lens used in the Loeux mirror interferometry system is smaller than the minimum size parameter of the outgoing beam mentioned above, the wavelength of the laser beam used by the Loeux mirror interferometry system to fabricate the required grating is calculated based on the minimum size parameter of the outgoing beam, the grating area of ​​the required grating, and the grating period of the required grating.

[0107] For example, the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the desired grating can be calculated using the following formula:

[0108] ;

[0109] in, This indicates the required grating width. The grating period represents the required grating. This represents the minimum size parameter of the emitted beam. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system to create the required grating.

[0110] For example, formula (2) above can be obtained through the following steps:

[0111] P1 determines the first correlation between the grating period of the required grating, the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn interferometry exposure system when making the required grating.

[0112] For example, this can be achieved through the following formula:

[0113] ;

[0114] in, The grating period represents the required grating. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the required grating. The refractive index of the propagation medium is used in air. , This indicates the interference angle of the exposed beam.

[0115] P2 determines the second correlation between the required grating width and the length of the Loe mirror used in the Loe mirror interference exposure system, as well as the interference angle of the exposure beam.

[0116] For example, this can be achieved using the following formula:

[0117] ;

[0118] in, This indicates the required grating width. This indicates the length of the Loewe mirror used in the Loewe mirror interferometry exposure system. This indicates the interference angle of the exposed beam.

[0119] Based on the first and second association relationships mentioned above, P3 calculates formula (2).

[0120] That is, by combining the above formulas (4) and (5) into a single relational expression, we can obtain formula (2).

[0121] For example, formula (3) above can be obtained through the following steps:

[0122] T1 determines the first correlation between the grating period of the required grating and the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn interferometry exposure system when making the required grating.

[0123] For example, this can be achieved using the following formula:

[0124] ;

[0125] in, The grating period represents the required grating. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the required grating. Indicates the spatial refractive index, in air, , This indicates the interference angle of the exposed beam.

[0126] Combining formula T2 (1) with the first correlation, we get formula (3).

[0127] That is, by combining the above formulas (4) and (1), we can obtain formula (3).

[0128] For the interference field formed by the Loewe mirror interferometric exposure system described above, the exposure contrast on the grating substrate surface reaches its maximum when the polarization directions of the first and second exposure beams are consistent and parallel to the grating lines on the grating substrate. Therefore, to obtain the maximum exposure contrast, both the first and second exposure beams should use S-polarized light (i.e., TE-polarized light).

[0129] therefore,

[0130] For example, formula (4) can be obtained through the following steps:

[0131] K1 determines the beam electric field of the two exposure beams in the Loehr mirror interferometric exposure system.

[0132] like Figure 4The diagram shows a schematic of a Loewe mirror interferometric exposure system using S-polarized light to perform interferometric exposure on a grating substrate. When the first and second exposure beams, as S-polarized light, interfere at an angle on the grating substrate, the light wave vectors of the first and second exposure beams are perpendicular to the plane of the paper. The electric field E1 of the first exposure beam and the electric field E2 of the second exposure beam can be obtained using the following formula:

[0133] ;

[0134] in, This represents the electric field of the first exposure beam. This represents the electric field of the second exposure beam. Indicates the lateral extension direction of the grating substrate. This indicates the interference angle of the first or second exposure beam. This represents the imaginary unit in Euler's formula. This represents the light wave vector of the first or second exposure beam. The refractive index of the propagation medium is used in air. , Indicates wavelength.

[0135] K2 determines the total light wave of the two exposure beams in the Loeux mirror interferometric exposure system based on the beam electric fields of the two exposure beams mentioned above.

[0136] For example, this can be achieved using the following formula:

[0137] ;

[0138] in, This represents the total wavelength of the two exposure beams. This represents the electric field of the first exposure beam. This represents the electric field of the second exposure beam.

[0139] K3 determines the light intensity distribution value formed by the mutual interference of the two exposure beams in the Loe mirror interferometric exposure system based on the total light wave mentioned above.

[0140] For example, this can be achieved through the following formula:

[0141] ;

[0142] in, This represents the light intensity distribution value formed by the interference of two exposure beams in a Loehr interferometer exposure system. This represents the total wavelength of the two exposure beams. This represents the electric field of the first exposure beam. The electric field of the second exposure beam. This represents the light wave vector of the first or second exposure beam. Indicates the lateral extension direction of the grating substrate. This indicates the interference angle of the first or second exposure beam.

[0143] Based on the above light intensity distribution values, K4 is calculated to obtain formula (4).

[0144] For example, it includes the following steps:

[0145] In the process of grating slot shape control, in order to improve the control accuracy of the grating slot shape and shorten the exposure time, it is necessary to control the light intensity of the two exposure beams in the Loehn mirror interferometric exposure system to be the same. Therefore, based on the premise that the light intensity of the two exposure beams in the Loehn mirror interferometric exposure system is the same, the above is obtained. .

[0146] by replace and Substituting into formula (10), we obtain the above.

[0147] ;

[0148] Substituting formula (8) into formula (11), we obtain the following... .

[0149] Will Substituting into formula (12), we obtain the following... .

[0150] Based on formula (13), the interference intensity of the two exposure beams is determined to be interference fringes with periodic distribution along the direction, and the interference fringe period is obtained. .

[0151] Since the grating period is equal to the interference fringe period, then .

[0152] For the Loehn-guided interferometry exposure system, the exposure operation of the grating substrate using a laser beam of the aforementioned wavelength is exemplified by the following steps:

[0153] The laser emits a laser beam of the aforementioned wavelength. After passing through a spatial filter, the laser beam becomes a spherical wave and reaches a collimating lens. After collimation by the collimating lens, it becomes a parallel beam.

[0154] A portion of the parallel beam is used as the first exposure beam to illuminate the Loe mirror. After being reflected by the Loe mirror, it is used as the first exposure beam to illuminate the direction of the grating substrate fixture. The other portion of the parallel beam is used as the second exposure beam to illuminate the direction of the grating substrate fixture.

[0155] The angle between the first and second exposure beams is adjusted by rotating the base so that the period of the interference fringes in the interference field formed by the first and second exposure beams meets the grating period requirements of the desired grating.

[0156] A grating substrate with spin-coated photoresist is fixed on a grating substrate fixture, and the photoresist on the grating substrate is subjected to interference exposure within the aforementioned interference field.

[0157] As a preferred embodiment, the laser in the Loewe mirror interferometry system is preferably a wavelength-tunable semiconductor laser. This allows the wavelength of the laser beam to be adjusted by the wavelength-tunable semiconductor laser without changing the original interference optical path, thereby enabling the fabrication of gratings with different periods and improving the fabrication efficiency of the desired gratings.

[0158] For example, wavelength-tunable semiconductor lasers can be external cavity tunable lasers, vertical cavity surface-emitting tunable lasers based on microelectromechanical systems, distributed feedback lasers, distributed Bragg reflector lasers, etc.

[0159] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. An exposure method for fabricating gratings, characterized in that, Includes the following steps: Based on the required grating area, the required grating period, and the wavelength of the laser beam currently used in the Loeux mirror interferometry system, determine the minimum size parameters of the output beam of the collimating lens of the Loeux mirror interferometry system under the size of the Loeux mirror used. Determine whether the size of the outgoing beam from the collimating lens used in the Loehr interferometric exposure system is not less than the minimum size parameter of the outgoing beam; If the size of the outgoing beam of the collimating lens used in the Loe mirror interferometry system is not less than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loe mirror interferometry system to fabricate the required grating is calculated based on the size of the Loe mirror, the grating area of ​​the required grating, and the grating period of the required grating. If the size of the outgoing beam of the collimating lens used in the Loeux mirror interferometry system is smaller than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loeux mirror interferometry system to fabricate the required grating is calculated based on the minimum size parameter of the outgoing beam, the grating area of ​​the required grating, and the grating period of the required grating. The Loewe mirror interferometric exposure system uses a laser beam of the specified wavelength to expose the grating substrate.

2. The exposure method for fabricating a grating according to claim 1, characterized in that, The minimum size parameter of the collimating lens output beam of the Loewe mirror interferometry system is determined based on the required grating area, the required grating period, and the wavelength of the laser beam currently used in the Loewe mirror interferometry system. This is specifically achieved through the following formula: ； in, This represents the minimum size parameter of the emitted beam. This indicates the required grating width. This indicates the grating period of the required grating. This indicates the wavelength of the laser beam currently used in the Loewe mirror interferometry exposure system.

3. The exposure method for fabricating a grating according to claim 1, characterized in that, If the size of the outgoing beam from the collimating lens used in the Loewe mirror interferometry system is not less than the minimum size parameter of the outgoing beam, then the wavelength of the laser beam used by the Loewe mirror interferometry system to fabricate the required grating is calculated according to the following formula, based on the size of the Loewe mirror used, the grating area of ​​the required grating, and the grating period of the required grating: ； in, This indicates the required grating width. This indicates the grating period of the required grating. This indicates the length of the Loewe mirror used in the Loewe mirror interferometry exposure system. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system to create the required grating.

4. The exposure method for fabricating a grating according to claim 2, characterized in that, If the output beam size of the collimating lens used in the Loewe mirror interferometry system is smaller than the minimum output beam size parameter, then the wavelength of the laser beam used by the Loewe mirror interferometry system to fabricate the required grating is calculated according to the following formula based on the minimum output beam size parameter, the grating area of ​​the required grating, and the grating period of the required grating: ； in, This indicates the required grating width. This indicates the grating period of the required grating. This represents the minimum size parameter of the emitted beam. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system to create the required grating.

5. The exposure method for fabricating a grating according to claim 3, characterized in that, Formula (2) is derived through the following steps: Determine the first correlation between the grating period of the required grating and the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interferometry exposure system when making the required grating; The second correlation between the required grating width and the length of the Loewe mirror used in the Loewe mirror interferometry exposure system and the interference angle of the exposure beam is determined; Based on the first and second association relationships, formula (2) is calculated.

6. The exposure method for fabricating a grating according to claim 5, characterized in that, The first correlation between the grating period of the required grating, the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interference exposure system for fabricating the required grating is achieved by the following formula: ； in, This indicates the grating period of the required grating. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the required grating. The refractive index of the propagation medium is used in air. , This indicates the interference angle of the exposed beam.

7. The exposure method for fabricating a grating according to claim 5, characterized in that, The second correlation between the required grating width, the length of the Loehn mirror used in the Loehn mirror interference exposure system, and the interference angle of the exposure beam is achieved through the following formula: ； in, This indicates the required grating width. This indicates the length of the Loewe mirror used in the Loewe mirror interferometry exposure system. This indicates the interference angle of the exposed beam.

8. The exposure method for fabricating a grating according to claim 4, characterized in that, Formula (3) is derived through the following steps: Determine the first correlation between the grating period of the required grating and the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interferometry exposure system when making the required grating; Formula (1) combined with the first correlation relationship yields formula (3).

9. The exposure method for fabricating a grating according to claim 8, characterized in that, The first correlation between the grating period of the required grating, the interference angle of the exposure beam, and the wavelength of the laser beam used in the Loehn mirror interference exposure system for fabricating the required grating is achieved by the following formula: ； in, This indicates the grating period of the required grating. This indicates the wavelength of the laser beam used in the Loehn mirror interferometry exposure system for fabricating the required grating. Indicates the spatial refractive index, in air, , This indicates the interference angle of the exposed beam.

10. The exposure method for fabricating a grating according to claim 6 or 9, characterized in that, The exposure beam uses S-polarized light.

11. The exposure method for fabricating a grating according to claim 10, characterized in that, Formula (4) is derived through the following steps: Determine the beam electric field of the two exposure beams in the Loehr mirror interferometric exposure system; The total light wave of the two exposure beams in the Loe mirror interferometric exposure system is determined based on the beam electric field of the two exposure beams. Based on the total light wave, determine the light intensity distribution value formed by the mutual interference of the two exposure beams in the Loe lens interferometric exposure system; Based on the light intensity distribution value, formula (4) is calculated.

12. The exposure method for fabricating a grating according to claim 11, characterized in that, The electric field of the two exposure beams in the Loehr mirror interferometric exposure system is determined by the following formula: ； in, This represents the electric field of the first exposure beam. This represents the electric field of the second exposure beam. Indicates the lateral extension direction of the grating substrate. This indicates the interference angle of the first or second exposure beam. This represents the imaginary unit in Euler's formula. This represents the light wave vector of the first or second exposure beam. The refractive index of the propagation medium is used in air. , Indicates wavelength.

13. The exposure method for fabricating a grating according to claim 12, characterized in that, The determination of the total light wave of the two exposure beams in the Loewe mirror interferometric exposure system based on the beam electric field of the two exposure beams is achieved by the following formula: ； in, This represents the total wavelength of the two exposure beams. This represents the electric field of the first exposure beam. This represents the electric field of the second exposure beam.

14. The exposure method for fabricating a grating according to claim 13, characterized in that, The determination of the light intensity distribution value formed by the mutual interference of two exposure beams in the Loe lens interferometric exposure system based on the total light wave is achieved by the following formula: ； in, This represents the light intensity distribution value formed by the interference of two exposure beams in a Loehr interferometer exposure system. This represents the total wavelength of the two exposure beams. This represents the electric field of the first exposure beam. The electric field of the second exposure beam. This represents the light wave vector of the first or second exposure beam. Indicates the lateral extension direction of the grating substrate. This indicates the interference angle of the first or second exposure beam.

15. The exposure method for fabricating a grating according to claim 14, characterized in that, The calculation of formula (4) based on the light intensity distribution value includes the following steps: Based on the fact that the two exposure beams in the Loehn mirror interferometry exposure system have the same light intensity, the following is obtained: ; by replace and Substituting into formula (10), we obtain the above. ; Substituting formula (8) into formula (11), we obtain the following: ; Will Substituting into formula (12), we obtain the following... ; Based on formula (13), the interference intensity of the two exposure beams is determined as along... Interference fringes with periodic directional distribution are used to obtain the interference fringe period. ; Since the grating period is equal to the interference fringe period, then .

16. The exposure method for fabricating a grating according to claim 1, characterized in that, The Loewe mirror system includes a laser, a spatial filter, a collimating lens, a Loewe mirror, a grating substrate fixture, and a rotating base; The Loe lens is perpendicular to the grating substrate clamp, with one end of the Loe lens in contact with one end of the grating substrate clamp. The Loe lens and the grating substrate clamp are fixed together on the rotating base; The right-angle region formed by the Loe lens and the grating substrate clamp faces the collimating lens.

17. The exposure method for fabricating a grating according to claim 16, characterized in that, The Loewe mirror interferometric exposure system uses a laser beam of the specified wavelength to expose the grating substrate, including the following steps: The laser emits a laser beam of the specified wavelength. After passing through a spatial filter, the laser beam becomes a spherical wave and reaches a collimating lens. After collimation by the collimating lens, it becomes a parallel beam. A portion of the parallel beam is used as the first beam to illuminate the Loe mirror. After being reflected by the Loe mirror, it is used as the first exposure beam to illuminate the direction of the grating substrate fixture. The other portion of the parallel beam is used as the second exposure beam to illuminate the direction of the grating substrate fixture. The angle between the first exposure beam and the second exposure beam is adjusted by rotating the base so that the period of the interference fringes in the interference field formed by the first exposure beam and the second exposure beam meets the grating period requirements of the required grating. A grating substrate with spin-coated photoresist is fixed on a grating substrate fixture, and the photoresist on the grating substrate undergoes interference exposure within the interference field.

18. The exposure method for fabricating a grating according to claim 16, characterized in that, The laser is a wavelength-tuned semiconductor laser.

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